Since the lever kinematics of the two lifting devices is identical, and only the machine part to be lifted is different, specifically machines for opening of tapping holes, or hood manipulators, the lifting system is described below only with reference to machines for opening of tapping holes.
After opening the tapping hole of a metallurgical furnace, the carriage with the tool, for example, the boring bar, must be moved as quickly as possible out of its working position via the runner away from the liquid metal stream flowing out of the furnace, in order not to be damaged by the liquid metal.
Nevertheless, the tool must be changed frequently due to wear. For this reason a bar changer is often available which as a robot removes the used tool, hereinafter called the boring bar, and inserts a new boring bar into the carriage from a storage magazine. To do this it is necessary that the carriage with the boring bar assume a neutral position which is always uniform and horizontal so that the bar changer can engage correctly.
Known lifting devices in which the angle of incline of the working position can be set do not satisfy these conditions for automatic boring bar changing, since an altered boring angle also causes an altered neutral position.